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1464 CYTOKINE LEVELS IN CYSTIC RENAL MASSES
growth factor (FGF-2) in renal cell carcinoma, which is indis- tinguishable from that in normal kidney, is involved in renal cell carcinoma growth. J. Urol., 152 1626, 1994.
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These authors measured the concentration of cytokines in cystic fluid associated with renal cell carcinoma and simple benign cysts, and found decreased concentrations of IG6 and basic fibroblast growth factor in the latter group. Based on these data they concluded that quantification of these cytokines in cystic fluids may be useful in
the preoperative diagnosis of malignant renal Cysts. The preopera. tive diagnosis of a complicated cystic lesion of the kidney may be difficult because it is neither clearly benign nor clearly malignant on imaging studies. The Bosniak classification of renal cysts provides a useful framework for the evaluation of these lesions.' Category I lesions are unequivocally benign on imaging studies and category Iv lesions are clearly malignant. Categories I1 and 111 range from minimally to more complicated cystic lesions and they are the Source of the diagnostic dilemma. Cyst puncture plus cytokine determina- tion is an interesting approach to the complex cystic lesion but the authors do not provide compelling data supporting its use. Based on their findings under what circumstances would they not explore a complex renal cystic mass? Although the differences in mean con- centrations were significant, there was also significant overlap among the groups.
From another interpretation of these data it could argued that such measurements are not useful at all. Of the 21 malignant lesions studied 13 were diagnosed preoperatively as cystic renal cell carci- noma and probably met the Bosniak criteria for a category IV cyst. Since the management of these lesions is clear, cytokine concentra- tions in the cystic fluid do not provide additional diagnostic informa- tion and including these tumors skews the results. In the remaining 8 malignant lesions IL-6 concentrations were low (average 8.6 pg./ ml.) in 6 (75%) and indistinguishable from benign cysts (basic fibro- blast growth factor data not provided). IL-6 levels in this group may be low because in the majority fluid aspiration was done of adjoining and closely situated cysts. False-negative results due to sampling error temper enthusiasm for radiographic renal cyst biopsy. Equiv- ocal results from cyst puncture under direct vision do not generate further excitement for this technique.
Joel B. Nelson Brady Urological Institute The Johns Hopkins Hospital Baltimore, Maryland
1. Bosniak, M. A.: The current radiographical approach to renal cysts. Radiology, 158 1, 1986.